Currently, most wheel-type heavy vehicles have a non-independent suspension with leaf springs and an oil-gas suspension as elastic elements, wherein left and right wheels of the non-independent suspension and tires thereof are fastened to a same axle and are connected to a vehicle frame or a vehicle body through the suspension. As such, the impact load transferred to the vehicle body from the ground cannot be effectively attenuated by the suspension, and hopping up and down of the two wheels can cause the vehicle to be tilted.
As to an independent suspension vehicle, its unsprung weight is low, and the impact load applied to the suspension and transferred to the vehicle body is relatively small, which is favorable to improving the ride comfort of the vehicle and ground contact performance of the tires; and hopping of the left and right wheels has no direct mutual influence, so tilting and vibration of the vehicle body can be reduced. At present, a suspension structure for an all-terrain crane chassis has been gradually replaced by an independent suspension structure. As an oil-gas independent suspension device has very good nonlinearity, the two wheels can move separately without mutual influence, the vehicle ride comfort is improved, and it can ensure that the vehicle has good ride comfort during no-load driving and full-load driving. Thus, independent suspension technology has been gradually applied to wheel-type heavy vehicles with high requirement on off-road performance.
In the case of an independent suspension vehicle, to ensure that each directive wheel may move independently relative to the vehicle frame without being influenced by the directive wheel on the other side of the same axle, a trapezoidal tie rod in a steering trapezoidal mechanism should be disconnected-type when a steering trapezoidal arm hops up and down along with a steering knuckle/axle wheel side, to reduce movement interference between the steering trapezoidal mechanism and a suspension guide mechanism.
Among those disconnected steering trapezoidal mechanisms available at present, some only depend on a torque output by one or more steering gears to drive left/right wheels of the vehicle for steering, and some depend on a torque provided by one steering gear and one steering assisting follower to drive the left/right wheels of the vehicle for steering. The disconnected steering trapezoidal mechanism described above only depending on the torque output by the steering gear or only depending on the torque output by the steering gear and the steering assisting follower to overcome a steering resistance moment from the ground is only suitable for motor off-road vehicles with a relatively low weight. There is not yet a relatively perfect steering system for a wheel-type heavy vehicle with high requirement on off-road performance.